1. Field of the Invention
The invention relates to operation state determining apparatus and method for determining the state of operation of a fuel cell battery formed by stacking a plurality of unit cells.
2. Description of the Related Art
A related-art apparatus for determining the state of operation of a fuel cell battery is disclosed in Japanese Patent Application Laid-Open Publication No. 6-310161. This apparatus determines that the amount of fuel gas has abnormally reduced, if the output voltage of at least one of the unit cells that form the fuel cell battery has dropped below a predetermined value. Then, the apparatus stops the operation of the fuel cell battery in order to protect the fuel cell battery.
The phenomenon that the output voltage of a unit cell drops below a predetermined value (i.e., an output voltage during an appropriate state of operation) occurs not only in the case where the fuel gas has abnormally reduced, that is, the fuel gas is insufficient in amount, but also in the case where the oxidizing gas is insufficient in amount, the case where a solid electrolyte membrane of a unit cell becomes excessively dry (dried-up state), and the case where a fuel gas channel or an oxidizing gas channel of a unit cell has water droplets (flooded state). Therefore, mere detection of the output voltage of a unit cell decreasing below the predetermined value does not allow detailed knowledge of the state of operation of the fuel cell battery.
The invention has been accomplished in view of the aforementioned problems. It is an object of the invention to provide operation state determining apparatus and method that allow acquisition of detailed knowledge of the state of operation of a fuel cell battery.